Referential amplifier devices and methods of use thereof

ABSTRACT

A referential amplifier device includes an input port configured to be electrically coupled to a source to receive an input signal from the source at an input voltage level. A first current path system is coupled to the input port and comprises a first transconductor device, a third transconductor device, a first resistor device, and a second resistor device. A second current path system is in parallel with the first current path system and comprises a second transconductor device and a fourth transconductor device. A current level in the second transconductor device is set equal to a current level in the first transconductor device, and a current level in the second transconductor device is set equal to a current level in the fourth transconductor device. An output port is coupled to the second current path system and configured to provide an output voltage based on a difference between the input voltage level and a threshold voltage level for the referential amplifier device. A method of making the referential amplifier device is also disclosed.

FIELD

The present technology relates to a referential amplifier device for usein integrated circuit devices and methods of use thereof.

BACKGROUND

Many implantable energy harvesting and internet of things (IoT)applications require fundamental building blocks, such as bandgaps,amplifiers, and comparators. These elements must be designed for lowpower consumption and small die area. However, low power analogcircuitry often requires significant die area due to the very largeresistors that are needed to generate the bias and feedback voltagesneeded in many analog circuits. This is often overcome by using complexsystems composed of smaller high current elements that are operated at alow on-time duty cycle together with sample and hold circuitry to reducethe average current draw.

For example, FIG. 1 illustrates a prior art referential amplifier device10. The referential amplifier device 10 in this example includes abandgap voltage reference 12 that is coupled to a differential amplifier(gm stage) 14 or comparator. The bandgap voltage reference 12 iscompared to an input voltage (VIN) 16 via a resistor feedback divider 18and provides an output. The referential amplifier device 10 has a numberof disadvantages when employed in low power systems.

First, the referential amplifier device 10 requires a high current levelfor operation. The approach illustrated in FIG. 1 requires 6 seriescurrent paths to support the bandgap reference 12, the differentialamplifier 14, and the resistor feedback divider 18. Second, thereferential amplifier device 10 shown in FIG. 1 consumes a large diearea. In particular, the die area is made large by the need to employlarger resistors in the bandgap reference 12 and the resistor feedbackdivider 18, as the physical size of an integrated resistor (based onresistance employed) is inversely proportional to the power dissipatedin the resistor as given by the following equation.

P=V ² /R  (1)

where P is the power dissipated, V is the voltage, and R is theresistance. Third, the bandgap reference 12 requires a start-up circuit,which requires additional current and larger resistors. The bandgapreference 12 has two stable states of operation (V_(BG)=0 andV_(BG)=˜1.2V). However, the V_(BG)=0 state must be avoided whichrequires employing the additional current and large resistors, whichincreases die area.

SUMMARY

A referential amplifier device includes an input port configured to beelectrically coupled to a source to receive an input signal from thesource at an input voltage level. A first current path system is coupledto the input port and comprises a first transconductor device, a thirdtransconductor device, a first resistor device, and a second resistordevice. A second current path system is in parallel with the firstcurrent path system and comprises a second transconductor device and afourth transconductor device. A current level in the secondtransconductor device is set equal to a current level in the firsttransconductor device, and a current level in the second transconductordevice is set equal to a current level in the fourth transconductordevice. An output port is coupled to the second current path system andconfigured to provide an output voltage based on a difference betweenthe input voltage level and a threshold voltage level for thereferential amplifier device.

A method of making a referential amplifier device includes providing aninput port configured to be electrically coupled to a source to receivean input signal from the source at an input voltage level. A firstcurrent path system comprising a first transconductor device, a thirdtransconductor device, a first resistor device, and a second resistordevice is coupled to the input port. A second current path system isprovided in parallel with the first current path system and comprises asecond transconductor device and a fourth transconductor device. Acurrent level in the second transconductor device is set equal to acurrent level in the first transconductor device, and a current level inthe second transconductor device is set equal to a current level in thefourth transconductor device. An output port is coupled to the secondcurrent path system and configured to provide an output voltage based ona difference between the input voltage level and a threshold voltagelevel for the referential amplifier device.

The disclosed referential amplifier circuit advantageously provides alow current building block that may be used as a bandgap reference,differential amplifier, or comparator. In differential amplifier andcomparator mode a bandgap is advantageously not needed. The referentialamplifier circuit achieves an adjustable reference voltage at bandgaplevel accuracies without explicitly including a bandgap voltagereference. The disclosed approach reduces the required current and diearea by combining amplifier, comparator, and bandgap principals toprovide an ultra-low power, low-area solution. Examples of the presenttechnology further eliminate the need for a start-up circuit. Thedisclosed referential amplifier circuit may be employed, by way ofexample only, in battery chargers, in low power energy harvestingapplications, IoT devices, and medical implant integrated circuits.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of a prior art referential amplifiercircuit.

FIG. 2A is a circuit diagram of an exemplary referential amplifierdevice of the present technology.

FIG. 2B is a circuit diagram of an exemplary high gain referentialamplifier device of the present technology.

FIG. 3 illustrates one exemplary application of the referentialamplifier device of the present technology in a power management system.

FIG. 4 illustrates another exemplary application of the referentialamplifier device of the present technology in a mono-stablemultivibrator.

FIG. 5 illustrates yet another exemplary application of the referentialamplifier device of the present technology in a shunt regulator.

FIG. 6 illustrates a further exemplary application of the referentialamplifier device of the present technology in a delay timer.

FIG. 7 illustrates another exemplary application of the referentialamplifier device of the present technology in a series-pass regulator.

FIG. 8 illustrates yet another exemplary application of the referentialamplifier device of the present technology in a battery charger.

FIGS. 9-16 illustrate exemplary test bench date for a referentialamplifier device of the present technology.

DETAILED DESCRIPTION

An example of a referential amplifier device 200(1) is illustrated inFIG. 2A. In this particular example, the referential amplifier device100 includes two parallel current path systems 201 and 202, input port203, a ground 204, an output port 205, first and second transconductordevices 206(1) and 206(2), third and fourth transconductor devices207(1) and 207(2), and resistor devices 208(1) and 208(2), although thereferential amplifier device 200(1) may include other types and/ornumbers of elements or components in other configurations, such as theadditional components of referential amplifier device 200(2) illustratedand described with respect to FIG. 2B below, which provides a high gainversion of the present technology. Referring again to FIG. 2A, in thisexample a more simplified low gain version of a referential amplifierdevice 200(1), is employed.

The present technology provides a number of advantages includingproviding a low current referential amplifier device that requires onlytwo current paths for operation. Examples of this technology do notrequire a bandgap reference or a feedback voltage divider for operation,which both require larger resistance elements, which allows for asmaller die area for the referential amplifier device. Further, theremoval of the bandgap reference eliminates the requirement for astart-up circuit, which reduces the current level and reduces therequired die area. The referential amplifier device 200(1) of thepresent technology may be employed in a number of applications asdescribed in further detail below.

Referring again to FIG. 2A, the referential amplifier device 200(1)includes two parallel current path systems comprising a first currentpath system 201 and a second current path system 202 that provide anoutput that responds to the difference between the input voltage levelfor the referential amplifier device 200(1) and an intrinsic voltagereference (or threshold voltage) inherent to the circuit bias topologyof the referential amplifier device 200(1), as described in furtherdetail below.

Input port 203 is configured to be coupled to a source that providescurrent to operate the circuit of the referential amplifier device200(1). Input port 203 is coupled to both the first and second currentpath systems 201 and 202, which are in parallel. In one example, thecurrent required to operate the circuit is approximately 200 nA,although other operational current levels may be employed depending onthe operation. The input port 203 also provides a voltage level (V_(IN))at the input port 203 that is employed for differential signalmeasurements as described in further detail below. The ground 204 iscoupled to both of the parallel current path systems 201 and 202 andprovides a ground return for the circuit of the referential amplifierdevice 200(1).

The output port 205 is provided along the second current path system 202and provides an output current (I_(OUT)) and output voltage (V_(OUT))for the referential amplifier device 200(1) as described in furtherdetail below. The output current (I_(OUT)) and output voltage (V_(OUT))are responsive to the difference between the input voltage (V_(IN))provided to the input port 203 and the intrinsic reference (threshold)voltage (V_(REF)) of the referential amplifier device 200(1).

In this example, the referential amplifier device 200(1) includes firstand second transconductor devices 206(1) and 206(2), which are locatedalong the first and second current path systems 201 and 202,respectively. The referential amplifier device 200(1) also includesthird and fourth transconductor devices 207(1) and 207(2), which arelocated along the first and second current path systems 201 and 202,respectively, although other numbers of transconductor devices may beemployed, such as in the referential amplifier device 200(2) illustratedin FIG. 2B and discussed in further detail below. In this example, thetransconductor devices 206(1), 206(2), 207(1), and 207(2) are configuredto perform voltage-to-current conversion and may be employ any type ofFET. In this example, transconductor devices 206(1) and 206(2) and207(1) and 207(2) are selected from transistor devices that can beutilized to tune the threshold reference voltage (V_(REF)) of thereferential amplifier device 200(1). By way of example, transconductordevices 206(1) and 206(2) and 207(1) and 207(2) can be selected fromcore, high voltage, low voltage, high threshold, low threshold, etc.transistor devices in order to tune the reference (threshold) voltage(V_(REF)) of the referential amplifier device 200(1). In this example,transconductor devices 206(1) and 206(2) are negative gaintransconductor devices, while transconductor devices 207(1) and 207(2)are positive gain transconductor devices.

The referential amplifier device 200(1) in this example also includesresistor devices 208(1) and 208(2) located along the first current pathsystem 201, although other numbers of resistors may be employed. Thevalue of the resistors 208(1) and 208(2) are selected such that the sumof the complimentary to absolute temperature terms (CTAT) terms of thereferential amplifier device 200(2) equals the sum of the proportionalto absolute temperature (PTAT) terms, which results in the threshold(V_(REF)) or trip point of the referential amplifier device 200(1) beingindependent of temperature. Further, the resistors 208(1) and 208(2) inthis example provide the total resistance in the first current pathsystem 201 (bias leg) and are set to a prescribed total resistance toeliminate the temperature variation in the threshold (V_(REF)) forregulation, or in a comparator application, the trip point of thecomparator. The voltage drop across the resistor 208(2) provides thegate drive for the third transconductor device 207(1), which is lowerthan the gate drive to the fourth transconductor device 207(2), and thegate drive difference is equal to the voltage drop across the resistor208(2), as described in further detail below.

Referring now to FIG. 2B, another exemplary referential amplifier device200(2) is illustrated. This example provides a high gain version of thepresent technology. The referential amplifier device 200(2) is similarin structure and operation to the referential amplifier device 200(1)except as described below. Referring again to FIG. 2B, in this examplethe referential amplifier device 200(2) also includes the first currentpath system 201 and the second current path system 202 in parallel thatprovide an output that responds to the difference between the inputvoltage level for the referential amplifier device 200(2) and anintrinsic voltage (threshold) reference inherent to the circuit biastopology of the referential amplifier device 200(2).

Input port 203 is configured to be coupled to a source that providescurrent to operate the circuit of the referential amplifier device200(2). Input port 203 is coupled to both the first and second currentpath systems 201 and 202. In one example, the current required tooperate the circuit is approximately 200 nA, although other operationalcurrent levels may be employed. The input port 203 also provides avoltage level (V_(IN)) at the input port 203 that is employed fordifferential signal measurements as described in further detail below.The ground 204 is coupled to both of the parallel first and secondcurrent paths 201 and 202 and provides a ground return for the circuitof the referential amplifier device 200(2).

The output port 205 is provided along the second current path system 202and provides an output current (I_(OUT)) and output voltage (V_(OUT))for the referential amplifier device 200(2) as described in furtherdetail below. The output current (I_(OUT)) and output voltage (V_(OUT))are responsive to the difference between the input voltage (V_(IN))provided to the input port 203 and the intrinsic reference (threshold)voltage (V_(REF)) of the referential amplifier device 200(2).

In this example, the referential amplifier device 200(1) includes firstand second transconductor devices 206(1) and 206(2), which are locatedalong the first and second current path systems 201 and 202,respectively. The referential amplifier device 200(1) also includesthird and fourth transconductor devices 207(1) and 207(2), which arelocated along the first and second current path systems 201 and 202,respectively, although other numbers of transconductor devices may beemployed, such as in the referential amplifier device 200(2) illustratedin FIG. 2B and discussed in further detail below. In this example, thetransconductor devices 206(1), 206(2), 207(1), and 207(2) are configuredto perform voltage-to-current conversion and may be employ any type ofFET. In this example, transconductor devices 206(1) and 206(2) and207(1) and 207(2) are selected from transistor devices that can beutilized to tune the threshold reference voltage (V_(REF)) of thereferential amplifier device 200(1). By way of example, transconductordevices 206(1) and 206(2) and 207(1) and 207(2) can be selected fromcore, high voltage, low voltage, high threshold, low threshold, etc.transistor devices in order to tune the reference (threshold) voltage(V_(REF)) of the referential amplifier device 200(1). In this example,transconductor devices 206(1) and 206(2) are negative gaintransconductor devices, while transconductor devices 207(1) and 207(2)are positive gain transconductor devices.

In this example, the gain at the output port 205 is increased byemploying the first and third cascode devices 209(1) and 209(2) and thesecond and fourth cascode devices 210(1) and 210(2). In this example,cascode devices 209(1) and 210(2) are cascoded diode tied devices thathave their drain-source voltage drops complimentary to absolutetemperature (CTAT). Cascode devices 209(1) and 209(2) and cascodedevices 210(1) and 210(2) are selected from transistor devices that canbe utilized to tune the threshold reference voltage (V_(REF)) of thereferential amplifier device 200(2). By way of example, cascode devices209(1) and 2089(2) and cascode devices 210(1) and 210(2) can be selectedfrom core, high voltage, low voltage, high threshold, low threshold,etc. transistor devices in order to tune the reference (threshold)voltage (V_(REF)) of the referential amplifier device 200(2). In thisexample, cascode devices 209(1) and 210(1) are cascoded diode tieddevices that have their drain-source voltage drops complimentary toabsolute temperature (CTAT).

In this example, the resistor 208(1) is provided in segment 208(1a)-208(1 d), although other numbers of resistors may be employed. Inthis example, the segmented resistors 208(1 a)-208(1 d), as well as theresistor 208(2) are located along the first current path system 201. Thevalues of the resistors 208(1 a)-208(1 d) and 208(2) are selected suchthat the sum of the complimentary to absolute temperature terms (CTAT)terms of the referential amplifier device 200(2) equals the sum of theproportional to absolute temperature (PTAT) terms, which results in thethreshold (V_(REF)) or trip point of the referential amplifier device200(2) being independent of temperature. The resistors 208(1 a)-208(1 d)add to the series resistance in the first current path system 201 toprovide a gate bias voltage bias for the cascode devices 209(1), 209(2),210(1), and 210(2) to provide a high gain implementation of thereferential amplifier device 200(2). The area is not increased by addingthe segmented resistors 208(1 a)-208(1 d) because the total resistancein the first current path system 201 (bias leg) is set to a prescribedtotal resistance to eliminate the temperature variation in the threshold(V_(REF)) for regulation, or in a comparator application, the trip pointof the comparator. The voltage drop across the resistor 208(2) providesthe gate drive for the cascode device 210(1), which is lower than thegate drive to the cascode device 210(2), and the gate drive differenceis equal to the voltage drop across the resistor 208(2), as described infurther detail below.

An exemplary operation of the referential amplifier device 200(1) of thepresent technology will now be described with reference to FIG. 2A. Theoperation of the referential amplifier device 200(2) is similar but isconfigured to operate in a high gain mode, as described above.

Referring again to FIG. 2A, the referential amplifier device 200(1)receives an input voltage (V_(IN)) from a source coupled to the inputport 203. The source is selected based on the application of thereferential amplifier device 200(1), such as the exemplary applicationsdescribed below. V_(IN) provides current to operate the circuit. In oneexample, V_(IN) is approximately 200 nA and provides the voltage levelfor differential signal measurements, as described in further detailbelow.

The referential amplifier device 200(1) provides an output current(I_(OUT)) and output voltage V_(OUT) for the referential amplifierdevice 200(1) through the output port 205. The values for I_(OUT) isdefined by the following equation:

I _(OUT) =gm*(V _(IN) −V _(REF))  (2)

where gm is the voltage to current gain of the referential amplifierdevice 200(1), V_(IN) is the voltage provided to the input port 203, andV_(REF) is the intrinsic bandgap voltage reference (threshold) of thereferential amplifier device 200(1). The value for the thresholdreference voltage (V_(REF)) of the referential amplifier device 200(1)can be tuned based on the selection of the transconductor devices 206(1)and 206(2) and 207(1) and 207(2). By way of example, transconductordevices 206(1) and 206(2) and 207(1) and 207(2) can be selected fromcore, high voltage, low voltage, high threshold, low threshold, etc.transistor devices in order to tune the reference (threshold) voltage(V_(REF)) of the referential amplifier device 200(1). The voltage(V_(OUT)) is defined by the following equation:

V _(OUT) =gm*(V _(IN) −V _(REF))*R _(OUT)  (3)

where gm is the voltage to current gain of the referential amplifierdevice 200(1), V_(IN) is the voltage provided to the input port 203,V_(REF) is the intrinsic bandgap voltage reference of the referentialamplifier device 200(1), and R_(OUT) is the output impedance of thereferential amplifier device 200(1). Thus, the referential amplifier200(1) provides an output V_(OUT) that is dependent on the differencebetween the input voltage (V_(IN)) and the threshold voltage (V_(REF))similar to a bandgap reference. However, the referential amplifierdevice 200(1) does not require an explicit bandgap reference circuit,which reduces the complexity, current, and die area required for theproviding the voltage output (V_(OUT)).

Referring now to FIG. 2B, in this example, the gain at the output port205 is enhanced by including cascode devices 109(1), 109(2), 110(1), and110(2), as illustrated in FIG. 2B. The gate bias voltage for the cascodedevices is generated by segmenting the resistor 208(1) into resistors208(1 a)-208(1 d) such that the series resistance in the bias leg 201 ofthe referential amplifier device 200(2). The area is not increased byadding the segmented resistors 208(1 a)-208(1 d) because the totalresistance in the first current path system 201 (bias leg) is set to aprescribed total resistance to eliminate the temperature variation inthe threshold for regulation, or in the case of a comparator application(as described in further detail below), the trip point of thecomparator.

Referring again to FIG. 2A, the output at the output port 205 is at thecircuit trip point when the current in the third transconductor 206(2),which is set equal to the current in the first transconductor device206(1) by the PMOS weak inversion current mirror, equals the current inthe fourth transconductor device 207(2).

As the input voltage (V_(IN)) from the input port 203 increases frombelow the threshold (V_(REF)) of the referential amplifier device200(1), the output is low, and when input voltage (V_(IN)) exceeds thethreshold voltage (V_(REF)) of the referential amplifier device 200(1),the output provided at the output port 205 transitions from a low stateto a high state (0 to V_(IN)). As the input voltage (V_(IN)) voltagelevel increases the current in the second current path system 202 of thereferential amplifier device 200(1) increases, and as the current levelincreases, the voltage drop across the resistor 208(2) increases. Thevoltage drop across the resistor 208(2) provides the gate drive for thecascode device 110(1), which is lower than the gate drive to the thirdtransconductor device 207(1)), and the gate drive difference is equal tothe voltage drop across the resistor 208(2).

In this example, the transconductor devices 207(1) and 207(2) areoperated in weak inversion, which emulates the operation of a bipolartransistor. The area of the transconductor device 207(2) is x timeslarger than the area of the cascode transconductor device 207(1), and atthe threshold (V_(REF)) of the referential amplifier device 200(1), whenthe current through the transconductor devices 207(2) and 207(1) areequal, the current density of the transconductor device 207(1) is xtimes greater than the current densify of the transconductor device207(2).

There is an input voltage (V_(IN)) level provided to the input port 203where the voltage drop across the resistor 208(1) will result in thecurrent in the transconductor device 108(1) being equal to the currentin the transconductor device 108(2). This occurs when:

V_R6(T)=n*(k*T/q)*ln((W/L)_MN4/(W/L)_MN2)  (4)

where n is the weak inversion slope factor (˜1.4).

The voltage drop across the resistor 208(2) is proportional to current,which means that the current levels in both the first and second currentpath systems 201 and 202 of the referential amplifier device 200(1) atthe threshold level are proportional to absolute temperature (PTAT). Inthis example, the cascode devices 206(1) and 206(2) are cascoded diodetied devices, and their drain-source voltage drops are complimentary toabsolute temperature (CTAT). Since the current level at threshold isproportional to absolute temperature (PTAT), the temperature coefficientof the threshold level can be minimized by selecting the appropriateresistance in the first current path system 201 based on the values ofthe resistors 208(1) an d208(2), such that the sum of the CTAT termsequals the sum of the PTAT terms, which results in the threshold or trippoint of the referential amplifier device 200(1) being independent oftemperature.

A number of exemplary operations of the referential amplifier device200(1) will now be described with respect to FIGS. 3-8 , respectively.Although the examples are described with respect to referentialamplifier 200(1) it is to be understood that the high gain referentialamplifier 200(2) could be employed.

Referring now to FIG. 3 , in one example referential amplifier device200(1) can be employed in a comparator mode. Operating in comparatormode, the referential amplifier device 200(1) is employed for detectingwhen the input voltage (V_(IN)) exceeds or descends below the thresholdvoltage (V_(REF)). The referential amplifier device 200(1) can beutilized in this mode for example in power management systems thatrequire power on reset (POR) for reliable operation when powering updigital electronics. Referential amplifier device 200(1) can further beused to determine under voltage and over voltage situations in suchsystems. Under voltage levels must also be detected with low voltagealarm (LVA) to disable circuitry when supply levels are too low forreliable operation. Also, over voltage alarm (OVA) is required toprotect electronics from voltage stress or unreliable operation when thesupply voltage exceeds the voltage rating of the devices that comprisethe circuitry in the application.

Referring now to FIG. 4 , the referential amplifier device 200(1) can beused to create a temperature independent voltage threshold for amono-stable multivibrator circuit as illustrated in FIG. 4 . Themono-stable multivibrator circuit can be used to generate free runningclocks, by way of example only, which can be used by digital circuitryto sequence state machines. In this example, the RC network and thethreshold voltage (V_(REF)) of the referential amplifier device 200(1)set the frequency of the clock output as illustrated in FIG. 4 .

Referring now to FIG. 5 , in another example, the referential amplifierdevice 200(1) can be employed in a shunt regulator for an energyharvesting system. Shunt regulators are often needed in energyharvesting systems where the harvested power level may exceed the powerrequired by the application. When a capacitor or battery on the VREGnode of the shunt regulator, as illustrated in FIG. 5 , reaches themaximum allowable state of charge, excess receive energy must bedissipated. In this case the referential amplifier device 200(1) can beoperated in a linear mode to drive the gate of an NMOS shunt regulatorto dissipate excess energy, limiting VREG to a voltage that is no higherthan the threshold voltage (V_(REF)) of the referential amplifier device200(1).

Referring now to FIG. 6 , in a further example the referential amplifierdevice 200(1) can act as a delay path in comparator mode. In thisexample, the referential amplifier device 200(1) is used to detect whenthe RAMP signal exceeds the referential amplifier threshold levelvoltage (V_(REF)). The RC ramp charges up when IN is released (set tologic low). The RC time constant sets the rate of charge for thecapacitor, which in turn determines a delay from IN going low, and OUTgoing high. Delay timers are used to enable circuitry once a set timedelay has expired, allowing time for a circuit to reach a stableoperating point.

Referring now to FIG. 7 , in this example the referential amplifierdevice 200(1) can be used to create a temperature independent supplyvoltage that draws power from a supply that is greater than thethreshold voltage (V_(REF)) of the referential amplifier device 200(1).This topology is commonly called a series-pass regulator. In many energyharvesting applications, the analog circuitry requires a higher voltagesupply than the digital circuitry. The digital circuitry will often drawpower from the output of a series-pass regulator in order to lower thesupply voltage to a safe operating voltage for the digital electronics.

Referring now to FIG. 8 , operating in linear mode, the referentialamplifier device 200(1) of the present technology can be combined with ashunt transistor in a stacked configuration to prevent charge imbalancewhen charging series stacked batteries, as shown in FIG. 8 . Cellbalance during battery charging is commonly found in high voltageapplications, such as the batteries used to power motor vehicles, orenergy storage in solar or wind farm applications.

Although several exemplary applications are illustrated and described,it is to be understood that the referential amplifier device 200(1) orthe high gain referential amplifier device 200(2) of the presenttechnology could be employed in numerous other applications to providean output voltage that responds to differences between the input voltageand the threshold voltage of the circuit.

Examples

FIGS. 9-16 illustrate exemplary test bench data for a referentialamplifier device of examples of the present technology.

Having thus described the basic concept of the invention, it will berather apparent to those skilled in the art that the foregoing detaileddisclosure is intended to be presented by way of example only, and isnot limiting. Various alterations, improvements, and modifications willoccur and are intended to those skilled in the art, though not expresslystated herein. These alterations, improvements, and modifications areintended to be suggested hereby, and are within the spirit and scope ofthe invention. Additionally, the recited order of processing elements orsequences, or the use of numbers, letters, or other designationstherefore, is not intended to limit the claimed processes to any orderexcept as may be specified in the claims. Accordingly, the invention islimited only by the following claims and equivalents thereto.

What is claimed is:
 1. A referential amplifier device comprising: aninput port configured to be electrically coupled to a source to receivean input signal from the source at an input voltage level; a firstcurrent path system coupled to the input port and comprising a firsttransconductor device, a third transconductor device, a first resistordevice, and a second resistor device; a second current path system inparallel with the first current path system and comprising a secondtransconductor device and a fourth transconductor device, wherein acurrent level in the second transconductor device is set equal to acurrent level in the first transconductor device, and a current level inthe second transconductor device is set equal to a current level in thefourth transconductor device; and an output port coupled to the secondcurrent path system and configured to provide an output voltage based ona difference between the input voltage level and a threshold voltagelevel for the referential amplifier device.
 2. The referential amplifierdevice of claim 1, wherein the first current path system is configuredto have a resistance value that eliminates temperature variation in thethreshold voltage level.
 3. The referential amplifier device of claim 1,wherein the first transconductor device and the third transconductordevice are configured to have voltage drops that are complimentary toabsolute temperature.
 4. The referential amplifier device of claim 1,wherein the first current path system and the second current path systemare configured at the threshold voltage level to have current levelsthat are proportional to absolute temperature.
 5. The referentialamplifier device of claim 1, wherein the second transconductor deviceand the fourth transconductor device are configured to set the outputport at the threshold voltage level when a current level in the secondtransconductor device equals a current level in the fourthtransconductor device.
 6. The referential amplifier device of claim 1,wherein the third transconductor device and the fourth transconductordevice are configured to be operated in weak inversion.
 7. Thereferential amplifier device of claim 1 wherein the first current pathsystem further comprises a first cascode device and a third cascodedevice and the second current path system further comprises a secondcascode device and a fourth cascode device.
 8. The referential amplifierdevice of claim 7, wherein the first resistor comprises a plurality ofresistor segments configured provide a gate bias voltage for the first,second, third, and fourth cascode devices.
 9. The referential amplifierdevice of claim 8, wherein the first, second, third, and fourth cascodedevices and the plurality of resistor segments increase the voltage gainlevel at the output port.
 10. A method of making a referential amplifierdevice, the method comprising: providing an input port configured to beelectrically coupled to a source to receive an input signal from thesource at an input voltage level; coupling a first current path systemcomprising a first transconductor device, a third transconductor device,a first resistor device, and a second resistor device to the input port;providing a second current path system comprising a secondtransconductor device and a fourth transconductor device in parallel tothe first current path system, wherein a current level in the secondtransconductor device is set equal to a current level in the firsttransconductor device, and a current level in the second transconductordevice is set equal to a current level in the fourth transconductordevice; and coupling an output port to the second current path system,the output port configured to provide an output voltage based on adifference between the input voltage level and a threshold voltage levelfor the referential amplifier device.
 11. The method claim 10, wherein aresistance value in the first current path system is set to eliminatetemperature variation in the threshold voltage of the referentialamplifier device.
 12. The method of claim 10, wherein the firsttransconductor device and the third transconductor device have voltagedrops that are complimentary to absolute temperature.
 13. The method ofclaim 10, wherein current levels in the first current path system andthe second current path system at the threshold voltage are proportionalto absolute temperature.
 14. The method of claim 10, wherein thereferential device is at the threshold voltage when a current level inthe second transconductor device equals a current level in the fourthtransconductor device.
 15. The method of claim 10, wherein the thirdtransconductor device and the fourth transconductor device areconfigured to be operated in weak inversion.
 16. The method of claim 10further comprising: providing a first cascode device and a third cascodedevice located along the first current path system; and providing asecond cascode device and a fourth cascode device located along thesecond current path system.
 17. The method of claim 16, wherein thefirst resistor comprises a plurality of resistor segments configuredprovide a gate bias voltage for the first, second, third, and fourthcascode devices.
 18. The method of claim 17, wherein the first, second,third, and fourth cascode devices and the plurality of resistor segmentsincrease the voltage gain level at the output port.